Latex polymer

ABSTRACT

Herein is described a latex polymer derived from a composition comprising a cycloaliphatic monomer and an aromatic monomer, wherein the cycloaliphatic monomer comprises a cycloaliphatic (meth)acrylate monomer or a cycloaliphatic (meth)acrylamide monomer and the aromatic monomer comprises an aromatic (meth)acrylate monomer or an aromatic (meth)acrylamide monomer. Also described is an inkjet ink composition comprising the latex polymer.

BACKGROUND

Inkjet printing with aqueous inks is increasingly being used to print onnon-porous flexible and rigid media for signage and other printingapplications. It is recognized that inkjet printing of aqueous inks onnonporous media is substantially different than inkjet applications fortraditional porous paper-based media. On porous papers, ink dryingoccurs primarily by ink penetration into the media pore structure, andcontrol of image quality aspects is a strong function of the rate of inkpenetration into the media. Thus, optimization of the penetration rateis used for attributes such as optical density and color-to-color bleed.On nonporous media, there is no penetration of the ink into the media,i.e. the colorant remains on the surface of the media, and image qualitydefects resulting from wetting and ink migration across the nonporoussurface are more difficult to control, especially at high printingspeeds.

Durability of aqueous inks on nonporous substrates poses a challenge.Inks need to wet and adhere to a broad range of substrates, have goodabrasion and scratch resistance, resist attack by water, cleaningfluids, and solvents, and have good outdoor weatherability. There havebeen great improvements in the durability of aqueous ink-jet inksthrough incorporation of certain ink-jet compatible latex polymerdispersions made by emulsion polymerization. When printed as part of anink-jet ink, a latex component of the ink can form a film on a mediasurface, entrapping and protecting the colorant within the hydrophobicprint film.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of a printing system for use in an exampleof a method of printing.

DETAILED DESCRIPTION

Before the latex polymers, ink compositions, methods and related aspectsof the disclosure are disclosed and described, it is to be understoodthat this disclosure is not restricted to the particular processfeatures and materials disclosed herein because such process featuresand materials may vary somewhat. It is also to be understood that theterminology used herein is used for the purpose of describing particularexamples. The terms are not intended to be limiting because the scope isintended to be limited by the appended claims and equivalents thereof.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used herein, “co-polymer” refers to a polymer that is polymerizedfrom at least two monomers.

A certain monomer may be described herein as constituting a certainweight percentage of a polymer. This indicates that the repeating unitsformed from the said monomer in the polymer constitute said weightpercentage of the polymer.

If a standard test is mentioned herein, unless otherwise stated, theversion of the test to be referred to is the most recent at the time offiling this patent application.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be a littleabove or a little below the endpoint. The degree of flexibility of thisterm can be dictated by the particular variable.

As used herein, “latex,” “latex polymer,” or “latex particles” refer tothe polymeric masses synthesized from individual monomers, which can bedispersed in a liquid vehicle forming a latex dispersion. The term“latex” generally refers to liquid and polymeric particles that aredispersed within the liquid. However, when a latex (i.e. a latexdispersion including latex polymer particles) is formulated within anink, the liquid becomes part of the liquid vehicle of the ink, and thus,latex polymer can be described based on the latex particle or latexpolymer solids that remain dispersed in the liquid vehicle.

The term “monomer emulsion” refers to an organic monomer or monomer mixthat is emulsified in an aqueous or water phase. Once the organicmonomer or monomer mix is polymerized, a latex polymer dispersion isformed.

The term “latex polymer dispersion” or “latex dispersion” includes bothlatex particulates as well as the aqueous medium in which the latexparticulates are dispersed. More specifically, a latex dispersion is aliquid suspension comprising a liquid (such as water and/or otherliquids) and polymeric particulates from 20 nm to 500 nm (preferablyfrom 100 nm to 300 nm) in size (average particle size), and having aweight average molecular weight from about 10,000 Mw to 2,000,000 Mw(preferably from about 100,000 Mw to 300,000 Mw). Such polymericparticulates can comprise a plurality of monomers that are typicallyrandomly polymerized, and can also be crosslinked. When crosslinked, themolecular weight can be even higher than that cited above. The averageparticle size (e.g. volume or intensity weighted average particle size)may be determined by dynamic light scattering.

The term “non-porous” when referring to a substrate, such as a mediasubstrate, includes surfaces that can have relatively poor waterpermeability and absorption. Vinyl, polypropylene, polyethylene andother plastic sheets or films, metals, coated offset media, glass,certain woods, and other similar substrates are considered to benon-porous. The term “non-porous media” refers to print media which hasa Bristow Test of less than 2 ml/m² at a contact time of less than 0.5s. The Bristow Test is known in the art and is summarized below. A testspecimen of defined dimensions is affixed to the smooth rim of a wheelfree to rotate at a defined constant speed in contact with a stationarytest fluid applicator pressing against the test specimen with a definedpressure. The test fluid applicator consists of a test solution storagecompartment affixed above a 1 by 15-mm test fluid delivery slot, theslot being positioned so that the long dimension is perpendicular to thedirection of rotation of the rim of the wheel, and parallel to the wheelaxis. A defined quantity of test fluid is placed through the fluidreservoir, onto the fluid delivery slot. With the wheel with the testspecimen affixed rotating at constant speed, the test solutionapplicator is brought into contact with the rotating test specimen andheld in place under defined pressure. The test fluid is transferred fromthe test solution applicator onto the test specimen in a band whosewidth, controlled by the applicator slot width is approximately 15 mm,and whose length is function of the absorptive characteristics of thetest fluid interaction with the test specimen under the defined testconditions. The amount of liquid absorbed per unit area of test specimenis calculated from the volume of test fluid originally placed in theapplicator, and the average width and length of the band created on thetest specimen by the transferred test fluid. The time available for theliquid absorption is calculated from the volume of test fluid originallyplaced in the applicator and applicator geometry.

As used herein, “ink vehicle” refers to the liquid fluid in which alatex polymer and a pigment are placed to form an ink. Ink vehicles mayinclude a mixture of a variety of different agents, including, forexample, surfactants, solvents, co-solvents, buffers, biocides,viscosity modifiers, sequestering agents, stabilizing agents, humectantsand water.

The term “decap” is a measure of how long a printing nozzle may remaininactive before plugging and how many inkjet architecture firings arerequired to re-establish proper drop ejection.

The term “(meth)acrylate” is well understood in the art to refer to bothacrylates and methacrylates. For example, “cyclohexyl (meth)acrylate”refers to cyclohexyl acrylate and/or cyclohexyl methacrylate. Likewise,the term “cycloaliphatic (meth)acrylate monomer” denotes acycloaliphatic acrylate monomer and/or a cycloaliphatic methacrylatemonomer; and the term “aromatic(meth)acrylate monomer” denotes anaromatic acrylate monomer and/or an aromatic methacrylate monomer.

The term “(meth)acrylamide” is well understood in the art to refer toboth acrylamides and methacrylamides. For example, the term“cycloaliphatic (meth)acrylamide monomer” denotes a cycloaliphaticacrylamide monomer and/or a cycloaliphatic methacrylamide monomer; andthe term “aromatic (meth)acrylamide monomer” denotes an aromaticacrylamide monomer and/or an aromatic methacrylamide monomer.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not just the numerical valuesexplicitly recited as the end points of the range, but also to includeall the individual numerical values or sub-ranges encompassed withinthat range as if each numerical value and sub-range is explicitlyrecited. As an illustration, a numerical range of “about 1 wt % to about5 wt %” should be interpreted to include not just the explicitly recitedvalues of about 1 wt % to about 5 wt %, but also include individualvalues and subranges within the indicated range. Thus, included in thisnumerical range are individual values such as 2, 3.5, and 4 andsub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This sameprinciple applies to ranges reciting a single numerical value.Furthermore, such an interpretation should apply regardless of thebreadth of the range or the characteristics being described.

Unless otherwise stated, any feature described herein can be combinedwith any aspect or any other feature described herein.

While non-porous media for outdoor signage are typically PVC-based,which is relatively easy to adhere to with conventional latex inkjetinks, other non-porous media, e.g. rigid media, comprise a much greaterbreadth of media surface types, and many of these surfaces presentdifficult challenges for aqueous latex inks, such as adhesion tohydrophobic materials like polypropylene. Adhesion to low energysurfaces (e.g., polyethylene, polypropylene) has been found to beparticularly difficult. This problem has been encountered in manyindustries as the need to use inexpensive recyclable parts hasincreased.

Previous solutions to inkjet printing on a wide variety of non-poroussubstrates have employed primers which are applied to the non-porousmedia before printing. This requires significant operator interventionto ensure each substrate to be printed is completely primed with an evenprimer coating. Any defects in the application of the primer result inprint quality issues. Additionally such primers often containenvironmentally harsh solvents (e.g. cyclohexanone).

The present inventors have found difficulties with printing someexisting latex inkjet inks to some non-porous media, particularlynon-porous media with low energy surfaces, such as polypropylene andpolyethylene.

The present inventors have found that in order to print on a wide rangeof non-porous media in-printer ink drying and curing of inkjetcompositions should take place at a media temperature of about 70° C. orless, for example about 65° C. or less to avoid media deformation whichmay occur at higher temperatures. Therefore, the present inventors havesought to provide latex polymers and inkjet ink compositions comprisingsuch latex polymers which adhere to a wide range of substrates,particularly non-porous substrates, e.g. rigid and non-poroussubstrates, without the need for primer coating prior to printing of theinject inks and which also provide good decap performance and provideexcellent pigment binding resulting in excellent pigment retention uponenvironmental exposure.

In an aspect there is provided latex polymer derived from a compositioncomprising a cycloaliphatic monomer and an aromatic monomer, wherein thecycloaliphatic monomer comprises a cycloaliphatic (meth)acrylate monomeror a cycloaliphatic (meth)acrylamide monomer and the aromatic monomercomprises an aromatic (meth)acrylate monomer or an aromatic(meth)acrylamide monomer.

In another aspect there is provided an inkjet ink composition comprisinga latex polymer and an ink vehicle, wherein the latex polymer is derivedfrom a composition comprising a cycloaliphatic monomer and an aromaticmonomer, wherein the cycloaliphatic monomer comprises a cycloaliphatic(meth)acrylate monomer or a cycloaliphatic (meth)acrylamide monomer andthe aromatic monomer comprises an aromatic (meth)acrylate monomer or anaromatic (meth)acrylamide monomer.

In another aspect there is provided a method of inkjet printingcomprising: providing a non-porous print substrate; and inkjet printingan inkjet ink composition to the print substrate to form an ink layer onthe print substrate, wherein the inkjet ink composition comprises alatex polymer and an ink vehicle, wherein the latex polymer is derivedfrom a composition comprising a cycloaliphatic monomer and an aromaticmonomer, wherein the cycloaliphatic monomer comprises a cycloaliphatic(meth)acrylate monomer or a cycloaliphatic (meth)acrylamide monomer andthe aromatic monomer comprises an aromatic (meth)acrylate monomer or anaromatic (meth)acrylamide monomer.

Latex Polymer

Described herein is a latex polymer derived from a compositioncomprising a cycloaliphatic monomer and an aromatic monomer, wherein thecycloaliphatic monomer comprises a cycloaliphatic (meth)acrylate monomeror a cycloaliphatic (meth)acrylamide monomer and the aromatic monomercomprises an aromatic (meth)acrylate monomer or an aromatic(meth)acrylamide monomer. For example; the latex polymer may comprise acopolymer of a cycloaliphatic monomer and an aromatic monomer, whereinthe cycloaliphatic monomer comprises one or more monomers comprising acycloaliphatic (meth)acrylate monomer or a cycloaliphatic(meth)acrylamide monomer, and the aromatic monomer comprises one or moremonomers comprising an aromatic (meth)acrylate monomer or an aromatic(meth)acrylamide monomer. For example, the latex polymer may comprise acopolymer comprising cycloaliphatic monomer units (e.g. cycloaliphatic(meth)acrylate and/or cycloaliphatic (meth)acrylamide units) andaromatic monomer units (e.g. aromatic (meth)acrylate and/or aromatic(meth)acrylamide units).

The terms ‘cycloaliphatic’ and ‘aromatic’ are well understood by theskilled person.

In some examples, the cycloaliphatic monomer comprises a cycloaliphatic(meth)acrylate monomer or a cycloaliphatic (meth)acrylamide monomer. Insome examples, the cycloaliphatic monomer comprises a cycloaliphatic(meth)acrylate monomer. A cycloaliphatic (meth)acrylate monomer is amonomer comprising a cycloaliphatic moiety bonded to, either directly orindirectly, a (meth)acrylate moiety (e.g. by a carbon chain; for examplea substituted or unsubstituted carbon chain, for example a saturated orunsaturated carbon chain, such as a C₁₋₁₂ carbon chain, for example aC₁₋₁₀ carbon chain, a C₁₋₆ carbon chain, or a C₁₋₄ carbon chain, whereinone or more of the carbon atoms may be replaced by a heteroatom such asoxygen, nitrogen or sulfur, for example oxygen). In some examples, thecycloaliphatic monomer comprises a cycloaliphatic (meth)acrylamidemonomer. A cycloaliphatic (meth)acrylamide monomer is a monomercomprising a cycloaliphatic moiety bonded to, either directly orindirectly, a (meth)acrylamide moiety (e.g. by a carbon chain, forexample a saturated or unsaturated carbon chain, such as a C₁₋₁₂ carbonchain, for example a substituted or unsubstituted carbon chain, forexample a C₁₋₁₀ carbon chain, a C₁₋₆ carbon chain, or a C₁₋₄ carbonchain, wherein one or more of the carbon atoms may be replaced by aheteroatom such as oxygen, nitrogen or sulfur, for example oxygen).

In some examples, the cycloaliphatic moiety comprises a 5-12 memberedaliphatic ring, for example a carbon ring having 5-12 carbon atoms (e.g.a C₅-C₁₂ ring), or a 5-12 membered heteroaliphatic ring. In someexamples, the cycloaliphatic moiety comprises a C₅-C₁₂ ring, a C₅-C₁₂ring may be a single ring (such as cyclopentyl, cyclohexyl orcycloheptyl groups) or a bicyclic ring (such as decalin). In someexamples, the cycloaliphatic moiety comprises a 5-10 membered aliphaticring, for example a 6-10 membered aliphatic ring.

In some examples, the cycloaliphatic moiety comprises a carbon ringhaving 5-10 carbon atoms (e.g. a C₅-C₁₀ ring). In some examples, thecycloaliphatic moiety comprises a carbon ring having 6-10 carbon atoms(e.g. a C₆-C₁₀ ring).

In some examples, the cycloaliphatic moiety comprises a substituent,such as an alkyl, heteroalkyl, alkoxy, hydroxyl, cycloaliphatic oraromatic substituent. In some examples, the cycloaliphatic moietycomprises a substituent, such as an alkyl group (for example a C₁₋₁₂alkyl group, for example C₁₋₁₀ alkyl group, C₁₋₆ alkyl group, C₁₋₄ alkylgroup, or a methyl group), an aryl group (e.g. a C₅₋₁₂ aryl group, forexample C₅₋₁₀ aryl group), a heteroalkyl group (e.g. a C₁₋₁₂ heteroalkyl(such as ether containing group), for example C₁₋₁₀ heteroalkyl, C₁₋₈heteroalkyl, C₁₋₄ heteroalkyl (e.g. C₁₋₄ ether)). In some examples, thecycloaliphatic moiety is an optionally substituted cycloaliphaticmoiety, for example optionally substituted with a C₁₋₁₂ alkyl group.

In some examples, the aromatic monomer comprises an aromatic(meth)acrylate monomer or an aromatic (meth)acrylamide monomer. In someexamples, the aromatic monomer comprises an aromatic (meth)acrylatemonomer. An aromatic (meth)acrylate monomer is a monomer comprising anaromatic moiety bonded to, either directly or indirectly, a(meth)acrylate moiety (e.g. by a carbon chain, for example a substitutedor unsubstituted carbon chain, for example a saturated or unsaturatedcarbon chain, such as a C₁₋₁₂ carbon chain, for example a C₁₋₁₀ carbonchain, a C₁₋₆ carbon chain, or a C₁₋₄ carbon chain, wherein one or moreof the carbon atoms may be replaced by a heteroatom such as oxygen,nitrogen or sulfur, for example oxygen). In some examples, the aromaticmonomer comprises an aromatic (meth)acrylamide monomer. An aromatic(meth)acrylamide monomer is a monomer comprising an aromatic moietybonded to, either directly or indirectly, a (meth)acrylamide moiety(e.g. by a carbon chain; for example a substituted or unsubstitutedcarbon chain, for example a saturated or unsaturated carbon chain, suchas a C₁₋₁₂ carbon chain, for example a C₁₋₁₀ carbon chain, a C₁₋₆ carbonchain, or a C₁₋₄ carbon chain, wherein one or more of the carbon atomsmay be replaced by a heteroatom such as oxygen, nitrogen or sulfur, forexample oxygen).

In some examples, the aromatic moiety comprises a 5-12 membered aromaticring, for example an aromatic carbon ring having 6-12 carbon atoms (e.g.a C₆-C₁₂ ring), or a 5-12 membered heteroaromatic ring. In someexamples, the aromatic moiety comprises a C₅-C₁₂ aromatic ring, a C₅-C₁₂aromatic ring may be a single aromatic ring (e.g. benzyl or phenyl), ora bicyclic aromatic ring (e.g. naphthyl). In some examples, the aromaticmoiety comprises a 5-10 membered aromatic ring, for example a 6-10membered aromatic ring.

In some examples, the aromatic moiety comprises an aromatic carbon ringhaving 6-10 carbon atoms (e.g. a C₆-C₁₀ aromatic ring).

In some examples, the aromatic moiety comprises a substituent, such asan alkyl, heteroalkyl (including an ether containing group), alkoxy,hydroxyl, cycloaliphatic or aromatic substituent. In some examples, thearomatic moiety comprises a substituent. In some examples, the aromaticmoiety may be substituted by an alkyl group, (for example a C₁₋₁₂ alkylgroup, for example C₁₋₁₀ alkyl group, C₁₋₆ alkyl group, C₁₋₄ alkylgroup, or a methyl group), an aryl group (e.g. a C₅₋₁₂ aryl group, forexample C₅₋₁₀ aryl group), a heteroalkyl group (e.g. a C₁₋₁₂ heteroalkyl(such as ether containing group), for example C₁₋₁₀ heteroalkyl, C₁₋₆heteroalkyl, C₁₋₄ heteroalkyl (e.g. C₁₋₄ ether)). In some examples, thearomatic moiety is optionally substituted, for example optionallysubstituted with a C₁₋₁₂ alkyl group.

In some example, the cycloaliphatic monomer is a cycloaliphatic monomerhaving the formula (I)

wherein,R₁ is H or methyl;Z is O or NR₂, where R₂ is H, alkyl or X′;Y is a bond or a carbon chain, where one or more of the carbon atoms ofthe carbon chain may be replaced with a heteroatom such as oxygen,sulfur or nitrogen;X and X′ are independently cycloaliphatic moieties.

In some examples R₂ is alkyl, for example C₁₋₁₂, C₁₋₁₀, C₁₋₆, or C₁₋₄alkyl (e.g. methyl or ethyl). In some examples R₂ is an optionallysubstituted alkyl group. In some examples R₂ is H, an optionallysubstituted alkyl group or X′. In some examples, R₂ is H or X′. In someexamples, R₂ is H.

In some examples, Y is a bond or a saturated or unsaturated carbonchain. In some examples Y is a bond or a C₁₋₁₂, for example C₁₋₁₀, C₁₋₆,or C₁₋₄ carbon chain. In some examples, one or more of the carbon atomsof the carbon chain represented by Y is replaced with a heteroatomselected from oxygen, sulfur and nitrogen. In some examples, Y is abond.

In some examples, X is a 5-12 membered ring, for example a carbon ringhaving 5-12 carbon atoms (e.g. a C₅-C₁₂ ring), or a 5-12 memberedheteroaliphatic ring. In some examples, X is a C₅-C₁₂ single ring (suchas cyclopentyl, cyclohexyl or cycloheptyl groups) or a bicyclic ring(such as decalin).

In some examples, X is a carbon ring having 5-10 carbon atoms (e.g. aC₅-C₁₀ ring). In some examples, X is a carbon ring having 6-10 carbonatoms (e.g. a C₆-C₁₀ ring).

In some examples, X is substituted, for example with an alkyl, alkoxy,hydroxyl, heteroalkyl, cycloaliphatic or aromatic substituent. In someexamples, X is substituted with an alkyl group (for example a C₁₋₁₂alkyl group, for example C₁₋₁₀ alkyl group, C₁₋₆ alkyl group, C₁₋₄ alkylgroup, or a methyl group), an aryl group (e.g. a C₅₋₁₂ aryl group, forexample C₅₋₁₀ aryl group), a heteroalkyl group (e.g. a C₁₋₁₂ heteroalkyl(such as ether containing group), for example C₁₋₁₀ heteroalkyl, C₁₋₆heteroalkyl, C₁₋₄ heteroalkyl (e.g. C₁₋₄ ether)). In some examples, X isoptionally substituted, for example optionally substituted with a C₁₋₁₂alkyl group.

In some examples, X′ is a carbon ring having 5-12 carbon atoms (e.g. aC₅-C₁₂ ring), or a 5-12 membered heteroaliphatic ring. In some examples,X′ is a C₅-C₁₂ single ring (such as cyclopentyl, cyclohexyl orcycloheptyl groups) or a bicyclic ring (e.g a C6 or C10 fused ring, suchas decalin).

In some examples, X′ is a carbon ring having 5-10 carbon atoms (e.g. aC₅-C₁₀ ring). In some examples, X′ is a carbon ring having 6-10 carbonatoms (e.g. a C₆-C₁₀ ring).

In some examples, X′ is substituted, for example with an alkyl, alkoxy,hydroxyl, heteroalkyl, cycloaliphatic or aromatic substituent. In someexamples, X′ is substituted with an alkyl group (for example a C₁₋₁₂alkyl group, for example C₁₋₁₀ alkyl group, C₁₋₆ alkyl group, C₁₋₄ alkylgroup, or a methyl group), an aryl group (e.g. a C₅₋₁₂ aryl group, forexample C₅₋₁₀ aryl group), a heteroalkyl group (e.g. a C₁₋₁₂ heteroalkyl(such as ether containing group), for example C₁₋₁₀ heteroalkyl, C₁₋₆heteroalkyl, C₁₋₄ heteroalkyl (e.g. C₁₋₄ ether)). In some examples, X′is optionally substituted, for example optionally substituted with aC₁₋₁₂ alkyl group.

In some examples, for example when Z is NR₂ and R₂ is X′, X and X′ maybe the same.

Examples of cycloaliphatic monomers include: cyclohexyl acrylate,cyclohexyl methacrylate, methylcyclohexyl acrylate, methylcyclohexylmethacrylate, trimethylcyclohexyl acrylate, trimethylcyclohexylmethacrylate, and other cycloaliphatic methacrylate and acrylatemonomers including ester derivatives of decalinol, hydrogenatedbisphenol A and F. In some examples, the latex polymer comprises atleast about 50 wt % cycloaliphatic monomers by total weight solids ofthe latex polymer, for example at least about 55 wt %, or at least about60 wt % cycloaliphatic monomers by total weight solids of the latexpolymer.

In some examples, the latex polymer comprises up to about 95 wt %cycloaliphatic monomers by total weight solids of the latex polymer, forexample up to about 90 wt % cycloaliphatic monomers by total weightsolids of the latex polymer.

In some examples, the latex polymer comprises from about 50 wt % toabout 90 wt %, for example from about 60 wt % to about 90 wt %cycloaliphatic monomers by total weight solids of the latex polymer.

In some example, the aromatic monomer is an aromatic monomer having theformula (II)

wherein,R₁ is H or methyl;Z is O or NR₂, where R₂ is H, alkyl or W;Y is a bond or a carbon chain, where one or more of the carbon atoms ofthe carbon chain may be replaced with a heteroatom such as oxygen,sulfur or nitrogen;W and W′ are independently aromatic moieties.

In some examples R₂ is alkyl, for example C₁₋₁₂, C₁₋₁₀, C₁₋₈, or C₁₋₄alkyl (e.g. methyl or ethyl). In some examples R₂ is an optionallysubstituted alkyl group. In some examples R₂ is H, an optionallysubstituted alkyl group or W′. In some examples, R₂ is H or W′. In someexamples, R₂ is H.

In some examples, Y is a bond or a saturated or unsaturated carbonchain. In some examples Y is a bond or a C₁₋₁₂, for example C₁₋₁₀,C₁₋₁₀, C₁₋₈, or C₁₋₄ carbon chain. In some examples, one or more of thecarbon atoms of the carbon chain represented by Y is replaced with aheteroatom selected from oxygen, sulfur and nitrogen. In some examples,Y is a bond.

In some examples, W is a 5-12 membered aromatic ring, for example acarbon ring having 6-12 carbon atoms (e.g. a C₆-C₁₂ aromatic ring), or a5-12 membered heteroaromatic ring. In some examples W comprises a C₅-C₁₂aromatic ring, a C₅-C₁₂ aromatic ring may be a single aromatic ring(e.g. benzyl or phenyl) or a bicyclic aromatic ring (e.g a fused C6 orC10 aromatic ring, e.g. naphthyl). In some examples, W is a 5-10membered aromatic ring, for example a 6-10 membered aromatic ring.

In some examples, W is an aromatic carbon ring having 6-10 carbon atoms(e.g. a C₅-C₁₀ aromatic ring).

In some examples, W is substituted, for example W may be substitutedwith an alkyl group (for example a C₁₋₁₂ alkyl group, for example C₁₋₁₀alkyl group, C₁₋₆ alkyl group, C₁₋₄ alkyl group, or a methyl group), anaryl group (e.g. a C₅₋₁₂ aryl group, for example C₅₋₁₀ aryl group), aheteroalkyl group (e.g. a C₁₋₁₂ heteroalkyl (such as ether containinggroup), for example C₁₋₁₀ heteroalkyl, C₁₋₆ heteroalkyl, C₁₋₄ ether). Insome examples, W is optionally substituted, for example optionallysubstituted with a C₁₋₁₂ alkyl group.

In some examples, W is a 5-12 membered aromatic ring, for example acarbon ring having 6-12 carbon atoms (e.g. a C₆-C₁₂ aromatic ring), or a5-12 membered heteroaromatic ring. In some examples W′ comprises aC₆-C₁₂ aromatic ring, a C₆-C₁₂ aromatic ring may be a single aromaticring (e.g. benzyl or phenyl) or a bicyclic aromatic ring (e.g. a fusedC6 or C10 aromatic ring, e.g. naphthyl). In some examples, W′ is a 5-10membered aromatic ring, for example a 6-10 membered aromatic ring.

In some examples, W′ is an aromatic carbon ring having 6-10 carbon atoms(e.g. a C₆-C₁₀ aromatic ring).

In some examples, W is substituted, for example, W may be substitutedwith an alkyl group (for example a C₁₋₁₂ alkyl group, for example C₁₋₁₀alkyl group, C₁₋₆ alkyl group, C₁₋₄ alkyl group, or a methyl group), anaryl group (e.g. a C₅₋₁₂ aryl group, for example C₅₋₁₀ aryl group), aheteroalkyl group (e.g. a C₁₋₁₂ heteroalkyl (such as ether containinggroup), for example C₁₋₁₀ heteroalkyl, C₁₋₆ heteroalkyl, C₁₋₄ ether). Insome examples, W is optionally substituted, for example optionallysubstituted with a C₁₋₁₂ alkyl group.

In some examples, for example when Z is NR₂ and R₂ is W′, W and W′ maybe the same.

Examples of aromatic monomers include: 2-phenoxyethyl methacrylate,2-phenoxyethyl acrylate, phenyl propyl methacrylate, phenyl propylacrylate, benzyl methacrylate, benzyl acrylate, phenylethylmethacrylate, phenylethyl acrylate, benzhydryl methacrylate, benzhydrylacrylate, N-benzyl methacrylate, N-benzyl acrylate, N,N-diphenylmethacrylamide, N,N-diphenyl acrylamide, naphthyl methacrylate, naphthylacrylate, phenyl methacrylate and phenyl acrylate.

In some examples, the latex polymer comprises at least about 1 wt %aromatic monomers by total weight solids of the latex polymer, forexample at least about 2 wt %, or at least about 5 wt % aromaticmonomers by total weight solids of the latex polymer.

In some examples, the latex polymer comprises up to about 35 wt %aromatic monomers by total weight solids of the latex polymer, forexample up to about 30 wt %, up to about 25 wt %, or up to about 20 wt %aromatic monomers by total weight solids of the latex polymer.

In some examples, the latex polymer comprises from about 1 wt % to about35 wt % aromatic monomers by total weight solids of the latex polymer,for example from about 2 wt % to about 30 wt %, or about 5 wt % to about25 wt % aromatic monomers by total weight solids of the latex polymer.

In some examples, the latex polymer has a glass transition temperatureof about 20° C. or greater, for example about 30° C. or greater, about40° C. or greater, about 45° C. or greater, or about 50° C. or greater.

In some examples, the latex polymer has a glass transition temperatureof up to about 100° C., for example up to about 95° C., up to about 90°C., up to about 80° C., or up to about 70° C.

In some examples, the latex polymer has a glass transition temperaturein the range of about 20° C. to about 100° C., for example about 30° C.to about 90° C., about 50° C. to about 90° C., or about 55° C. to about70° C.

The glass transition temperature (Tg) of the latex polymer may beestimated using the Fox equation (T. G. Fox, Bull. Am. Physics Soc.,Volume 1, Issue No. 3, page 123 (1956)) using the Tg of the homopolymersof each of the monomers forming the copolymer of the latex polymer. Themaximum Tg of each of the homopolymers of each of the monomers making upto copolymer of the latex polymer may be taken from literature values(for example as listed in “Polymer Handbook”, edited by J. Brandrup, E.H. Immergut, and E. A. Grulke, Wiley Publishers, 4^(th) edition). Theglass transition temperature of the latex polymer may also be determinedusing DSC (differential scanning calorimetry) according to ASTM D3418.

In some examples, the composition from which the latex polymer isderived further comprises an alkyl meth(acrylate). In some examples, thecomposition from which the latex polymer is derived comprises an alkylmethacrylate monomer. In some examples, the composition from which thelatex polymer is derived comprises an alkyl acrylate monomer. In someexamples, the composition from which the latex polymer is derivedcomprises an alkyl acrylate monomer and an alkyl methacrylate monomer.In some examples, the alkyl (meth)acrylate may be a C₁₋₈ alkyl(meth)acrylate.

In some examples, the latex polymer comprises an alkyl meth(acrylate)component. In some examples, the latex polymer further comprises analkyl methacrylate component. In some examples, the latex polymerfurther comprises an alkyl acrylate component. In some examples, thelatex polymer further comprises an alkyl acrylate component and an alkylmethacrylate component.

In some examples, the latex polymer comprises from about 0 wt % to about10 wt %, for example from about 0.1 wt % to about 10 wt % of an alkylmeth(acrylate), for example methyl methacrylate.

In some examples, the latex polymer comprises a copolymer formed from analkyl meth(acrylate) monomer, a cycloaliphatic monomer and an aromaticmonomer. In some examples, the latex polymer comprises a copolymerformed from an alkyl meth(acrylate) monomer, (meth)acrylic acid, acycloaliphatic monomer and an aromatic monomer. In some examples, thelatex polymer comprises a copolymer formed from a (meth)acrylic acid, acycloaliphatic monomer and an aromatic monomer.

In some examples, the composition from which the latex polymer isderived further comprises an acid monomer, for example (meth)acrylicacid monomers or carboxylic acid monomers. In some examples, thecomposition from which the latex polymer is derived further comprises(meth)acrylic acid. For example, the composition may comprise(meth)acrylic acid in an amount of 0 wt % to about 15 wt %, about 0.1 wt% to about 15 wt %, for example, about 0.25 wt % to about 10 wt %, orabout 0.25 wt % to about 6 wt %. In some examples, the composition fromwhich the latex polymer is derived further comprises methacrylic acid.For example, the composition may comprise methacrylic acid in an amountof 0 wt % to about 15 wt %, about 0.1 wt % to about 15 wt %, forexample, about 0.25 wt % to about 10 wt %, or about 0.25 wt % to about 6wt %.

In some examples, the composition from which the latex polymer isderived further comprises an alkyl meth(acrylate) monomer and/or(meth)acrylic acid. In some examples, the composition from which thelatex polymer is derived further comprises an alkyl meth(acrylate)monomer and (meth)acrylic acid.

In some examples, the latex polymer substantially lacks a styrenecomponent. For example, the latex polymer may comprise less than about 5wt % styrene by total weight solids of the latex polymer, for exampleless than about 4 wt %, less than about 3 wt %, less than about 2 wt %,less than about 1 wt %, less than about 0.5 wt %, or less than about 0.1wt % styrene by total weight solids of the latex polymer. In someexamples, the latex polymer lacks a styrene component.

In some examples, the latex polymer may be prepared by copolymerizingthe monomer components with a copolymerizable surfactant (for examplesurfactants from the Hitenol® AR series or Hitenol® BC series, e.g.Hitenol® BC-10, BC-30, KH-05 or KH-10) to form a latex dispersion.

In some examples, the latex polymer is prepared by combining themonomers as an aqueous emulsion with an initiator. In some examples anysuitable polymer initiator may be used. In some examples, the initiatormay be selected from a persulfate, such as a metal persulfate or anammonium persulfate. In some examples, the initiator may be selectedfrom a sodium persulfate, ammonium persulfate or potassium persulfate.

A latex dispersion comprises latex polymer particles dispersed in water.

Inkjet Ink Composition

Described herein is an inkjet ink composition comprising a latex polymerand an ink vehicle, wherein the latex polymer is derived from acomposition comprising a cycloaliphatic monomer and an aromatic monomer,wherein the cycloaliphatic monomer comprises a cycloaliphatic(meth)acrylate monomer or a cycloaliphatic (meth)acrylamide monomer andthe aromatic monomer comprises an aromatic (meth)acrylate monomer or anaromatic (meth)acrylamide monomer. In some examples, the latex inkcomposition comprise a latex polymer, a pigment and an ink vehicle.

The latex polymer of the inkjet ink composition may be as describedabove.

In some examples, the inkjet ink composition comprises up to about 35 wt% pigment and latex polymer solids by total weight of the composition,for example up to about 30 wt %, about 25 wt % or up to about 20 wt %pigment and latex polymer solids by total weight of the composition.

In some examples, the inkjet ink composition comprises from about 0.5 wt% to about 35 wt % pigment and latex polymer solids by total weight ofthe composition, for example from about 1 wt % to about 30 wt %, fromabout 1 wt % to about 25 wt %, or from about 2 wt % to about 20 wt %pigment and latex polymer solids by total weight of the composition. Thepresent inventors have found that compositions having a total amount ofpigment and latex polymer solids within these ranges may be suitable forinkjet printing, for example for thermal inkjet printing.

In some examples, the inkjet ink composition comprises at least about 3wt % latex polymer by total weight of the composition, for example atleast about 5 wt % latex polymer by total weight of the composition. Insome examples, the inkjet ink composition comprises up to about 25 wt %latex polymer by total weight of the composition, for example up toabout 20 wt %, or up to about 15 wt % latex polymer by total weight ofthe composition. In some examples, the inkjet ink composition comprisesfrom about 3 wt % to about 25 wt %, for example about 5 wt % to about 25wt % latex polymer by total weight of the composition.

In some examples, the inkjet ink composition comprises at least about0.1 wt % pigment by total weight of the composition, for example, atleast about 0.3 wt % pigment by total weight of the composition. In someexamples, the inkjet ink composition comprises up to about 30 wt %pigment by total weight of the composition, for example, up to about 20wt % pigment by total weight of the composition, or up to about 15 wt %pigment by total weight of the composition. In some examples, the inkjetink composition comprises from about 0.1 wt % to about 30 wt %, forexample 0.3 wt % to about 30 wt % pigment by total weight of thecomposition.

In some examples, the inkjet ink composition comprises an amount ofpigment and an amount of latex polymer, such that the ratio of theamount of pigment to amount of latex by weight is in the range of about0.1:15 to 10:5.

In some examples, the inkjet ink composition substantially lacks astyrene component. For example, the inkjet ink composition may compriseless than about 5 wt % styrene by total weight solids of the latexpolymer, for example less than about 4 wt %, less than about 3 wt %,less than about 2 wt %, less than about 1 wt %, less than about 0.5 wt%, or less than about 0.1 wt % styrene by total weight solids of thelatex polymer.

Pigment

In some examples, the inkjet ink composition comprises a pigment. Forexample, the inkjet ink composition may comprise a latex polymer, apigment, and an ink vehicle.

In some examples, the inkjet ink composition is unpigmented orsubstantially lacks a pigment. For example, the inkjet ink compositionmay comprise less than 0.5 wt % of a pigment, for example less than 0.1wt % of a pigment or less than 0.05 wt % of a pigment by total weight ofthe composition. In some examples, the inkjet ink composition isunpigmented and lacks a pigment, for example the inkjet ink compositionmay be a colourless composition.

The term “pigment” can include particulate dispersible colorants thatcan be suspended or dispersed in a liquid vehicle in accordance withembodiments of the present invention. The pigment itself can be aself-dispersed pigment or a non-self-dispersed pigment.

The pigment may include black pigments, white pigments, cyan pigments,magenta pigments, yellow pigments, or the like. Suitable inorganicpigments include, for example, carbon black. However, other inorganicpigments may be suitable such as titanium oxide, cobalt blue(CoO—Al₂O₃), chrome yellow (PbCrO₄), and iron oxide. Suitable organicpigments include, for example, azo pigments including diazo pigments andmonoazo pigments, polycyclic pigments (e.g., phthalocyanine pigmentssuch as phthalocyanine blues and phthalocyanine greens, perylenepigments, perinone pigments, anthraquinone pigments, quinacridonepigments, dioxazine pigments, thioindigo pigments, isoindolinonepigments, pyranthrone pigments, and quinophthalone pigments), insolubledye chelates (e.g., basic dye type chelates and acidic dye typechelate), nitropigments, nitroso pigments, and the like. Representativeexamples of phthalocyanine blues include copper phthalocyanine blue andderivatives thereof (Pigment Blue 15). Representative examples ofquinacridones include Pigment Orange 48, Pigment Orange 49, Pigment Red122, Pigment Red 192, Pigment Red 202, Pigment Red 206, Pigment Red 207,Pigment Red 209, Pigment Violet 19 and Pigment Violet 42. Representativeexamples of anthraquinones include Pigment Red 43, Pigment Red 194(Perinone Red), Pigment Red 216 (Brominated Pyranthrone Red) and PigmentRed 226 (Pyranthrone Red). Representative examples of perylenes includePigment Red 123 (Vermillion), Pigment Red 149 (Scarlet), Pigment Red 179(Maroon), Pigment Red 190 (Red), Pigment Violet 19, Pigment Red 189(Yellow Shade Red) and Pigment Red 224. Representative examples ofthioindigoids include Pigment Red 86, Pigment Red 87, Pigment Red 88,Pigment Red 181, Pigment Red 198, Pigment Violet 36, and Pigment Violet38. Representative examples of heterocyclic yellows include PigmentYellow 1, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13,Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 65, Pigment Yellow73, Pigment Yellow 74, Pigment Yellow 151, Pigment Yellow 117, PigmentYellow 128 and Pigment Yellow 138, Pigment Yellow 155, Pigment Yellow83, and Pigment Yellow 213. Such pigments are commercially available ineither powder or press cake form from a number of sources including,BASF™ Corporation, Engelhard™ Corporation and Sun Chemical™ Corporation.

Examples of black pigments that can be used include carbon pigments. Thecarbon pigment can be almost any commercially available carbon pigmentthat provides acceptable optical density and print characteristics.Carbon pigments suitable for use in the present system and methodinclude, without limitation, carbon black, graphite, vitreous carbon,charcoal, and combinations thereof. Such carbon pigments can bemanufactured by a variety of known methods such as a channel method, acontact method, a furnace method, an acetylene method, or a thermalmethod, and are commercially available from such vendors as Cabot™Corporation, Columbian Chemicals Company, Degussa AG™, and E.I. DuPont™de Nemours and Company. Suitable carbon black pigments include, withoutlimitation, Cabot pigments such as MONARCH™ 1400, MONARCH™ 1300,MONARCH™ 1100, MONARCH™ 1000, MONARCH™ 900. MONARCH™ 880, MONARCH™ 800,MONARCH™ 700, CAB-O-JET™ 200, CAB-O-JET™ 300, REGAL™, BLACK PEARLS,ELFTEX™, MOGUL™, and VULCAN™ pigments; Columbian pigments such as RAVEN™7000, RAVEN™ 5750, RAVEN™ 5250, RAVEN™ 5000, and RAVEN™ 3500; Degussapigments such as Color Black FW200, RAVEN™ FW2, RAVEN™ FW2V, RAVEN™ FW1, RAVEN™ FW 18, RAVEN™ S160, RAVEN™ FW S170, Special Black™ 6, SpecialBlack™ 5, Special Black™ 4A, Special Black™ 4, PRINTEX™ U, PRINTEX™140U, PRINTEX™ V, and PRINTEX™140V.

Similarly, a wide variety of colored pigments can be used with theinkjet ink composition, therefore the following listing is not intendedto be limiting. For example, colored pigments can be blue, brown, cyan,green, white, violet, magenta, red, orange, yellow, as well as mixturesthereof. The following color dispersions are available from Cabot™ Corp.CABO-JET™ 250C, CABO-JET™ 260M, and CABO-JET™ 270Y The following colorpigments are available from BASF™ Corp.: PALIOGEN™ Orange, PALIOGEN™Orange 3040, PALIOGEN™ Blue L 6470, PALIOGEN™ Violet 5100, PALIOGEN™Violet 5890, PALIOGEN™ Yellow 1520, PALIOGEN™ Yellow 1560, PALIOGEN™ Red3871K, PALIOGEN™ Red 3340, HELIOGEN™ Blue L 6901F, HELIOGEN™ Blue NBD7010, HELIOGEN™ Blue K 7090, HELIOGEN™ Blue L 7101F, HELIOGEN™ BlueL6900, L7020, HELIOGEN™ Blue D6840, HELIOGEN™ Blue D7080, HELIOGEN™Green L8730, HELIOGEN™ Green K 8683, and HELIOGEN™ Green L 9140. Thefollowing pigments are available from Ciba-Geigy Corp.: CHROMOPHTAL™Yellow 3G, CHROMOPHTAL™ Yellow GR, CHROMOPHTAL™ Yellow 8G, IGRAZIN™Yellow 5GT, IGRALITE™ Rubine 4BL, IGRALITE™ Blue BCA, MONASTRAL™Magenta, MONASTRAL™ Scarlet, MONASTRAL™ Violet R, MONASTRAL™ Red B, andMONASTRAL™ Violet Maroon B. The following pigments are available fromHeubach Group™: DALAMAR™ Yellow YT-858-D and HEUCOPHTHAL™ Blue GXBT-583D. The following pigments are available from Hoechst SpecialtyChemicalsm: Permanent Yellow GR. Permanent Yellow G, Permanent YellowDHG, Permanent Yellow NCG-71, Permanent Yellow GG, Hansa Yellow RA,Hansa Brilliant Yellow 5GX-O2, Hansa Yellow-X, NOVOPERM™ Yellow HR,NOVOPERM™ Yellow FGL, Hansa Brilliant Yellow 10GX, Permanent YellowG3R-01, HOSTAPERM™ Yellow H4G, HOSTAPERM™ Yellow H3G, HOSTAPERM™ OrangeGR, HOSTAPERM™ Scarlet GO, HOSTAPERM™ Pink E, Permanent Rubine F6B, andthe HOSTAFINE™ series. The following pigments are available from MobayCorp.: QUINDO™ Magenta, INDOFAST™ Brilliant Scarlet, QUINDO™ Red R6700,QUINDO™ Red R6713, and INDOFAST™ Violet. The following pigments areavailable from Sun Chemical Corp.: L74-1357 Yellow, L75-1331 Yellow, andL75-2577 Yellow. Other examples of pigments can include Normandy MagentaRD-2400, Permanent Violet VT2645, Argyle Green XP-111-S, Brilliant GreenToner GR 0991, Sudan Blue OS, PV Fast Blue B2GO1, Sudan III, Sudan II,Sudan IV, Sudan Orange G, Sudan Orange 220, Ortho Orange OR 2673, LitholFast Yellow 0991 K, Paliotol Yellow 1840, Lumogen Yellow D0790,Suco-Gelb L1250, Suco-Yellow D1355, Fanal Pink D4830, Cinquasia Magenta,Lithol Scarlet D3700, Toluidine Red, Scarlet for Thermoplast NSD PS PA,E. D. Toluidine Red, Lithol Rubine Toner, Lithol Scarlet 4440, Bon RedC, Royal Brilliant Red RD-8192, Oracet Pink RF, Lithol Fast ScarletL4300, and white TIPURE R-101. These pigments are available fromcommercial sources such as Hoechst Celanese Corporation™, Paul Uhlich,BASF, American Hoechst™, Ciba-Geigy™, Aldrich™, DuPont™, Ugine Kuhlmanof Canada™, Dominion Color Company™, Magruder™, and Matheson™. Examplesof other suitable colored pigments are described in the Colour Index,3rd edition (The Society of Dyers and Colourists, 1982).

Ink Vehicle

The ink vehicle of the inkjet ink composition comprises water. Thewater, or a portion of the water, of the ink vehicle may be introducedto the ink vehicle as a latex polymer emulsion is combined with thefirst and second solvents of the ink vehicle. In some examples,additional water may be added to the inkjet ink composition.

The inkjet ink composition comprises water. In some examples, the inkjetink composition comprises at least about 20 wt %, for example at leastabout 30 wt %, at least about 40 wt %, or at least about 50 wt % bytotal weight of the composition. In some examples, the inkjet inkcomposition comprises up to about 90 wt % water, for example up to about85 wt %, up to about 80 wt %, or up to about 75 wt % by total weight ofthe composition. In some examples, the inkjet ink composition compriseswater in an amount from about 20 wt % to about 85 wt % by total weightof the inkjet ink composition, for example about 30 wt % to about 80 wt%, about 40 wt % to about 80 wt %, or from about 50% to about 75% water.

In some examples, the ink vehicle comprises water and a co-solvent (forexample a blend of co-solvents). In some examples, the inkjet inkcomposition comprises the co-solvent in an amount of at least about 1 wt%, for example at least about 5 wt %, or at least about 10 wt % by totalweight of the composition. In some examples, the inkjet ink compositioncomprises the co-solvent in an amount up to about 50 wt %, for exampleup to about 40 wt %, or up to about 35 wt % by total weight of thecomposition. In some examples the inkjet ink composition comprises aco-solvent in an amount of about 1 to about 50 wt % by total weight ofthe composition, for example from about 5 to about 40 wt % of thecomposition, or about 10 to about 35 wt % of the total weight of thecomposition.

In some examples, the ink vehicle comprises a co-solvent having aboiling point ranging from 160° C. to 285° C. In some examples, the inkvehicle comprises a co-solvent having a boiling point ranging from 170°C. to 250° C., for example from 170° C. to 220° C., or 170° C. to 215°C. In some examples, the ink vehicle comprises a co-solvent having aboiling point of about 215° C. or less.

In some examples, the co-solvent may be selected form organicco-solvents including aliphatic alcohols, aromatic alcohols, diols,glycol ethers, polyglycol ethers, caprolactams, formamides, acetamides,and long chain alcohols. In some examples, the co-solvent may beselected form primary aliphatic alcohols, secondary aliphatic alcohols,1,2-alcohols, 1,3-alcohols, 1,4-alcohols, 1,5-alcohols, ethylene glycolalkyl ethers, propylene glycol alkyl ethers, higher homologs (C₆-C₁₂) ofpolyethylene glycol alkyl ethers, pyrrolidinones, N-alkyl caprolactams,unsubstituted caprolactams, both substituted and unsubstitutedformamides, both substituted and unsubstituted acetamides, andcombinations thereof.

In some examples, the co-solvent comprises a first solvent having aboiling point of about 215° C. or less and a second solvent having aboiling point of at least about 220° C.

In some examples, the ink vehicle of the inkjet ink compositioncomprises a first solvent having a boiling point of about 212° C. orless, for example about 210° C. or less, for example about 205° C. orless. In some examples, the first solvent has a boiling point of atleast about 170° C., for example at least about 175° C., at least about180° C., or at least about 185° C. In some examples, the first solventhas a boiling point in the range of about 170° C. to about 215° C. Insome examples, the first solvent has a boiling point in the range ofabout 180° C. to about 215° C., for example about 185° C. to about 215°C., or about 185° C. to about 210° C.

In some examples, the first solvent is selected from an aliphaticalcohol, for example a primary aliphatic alcohol, a secondary aliphaticalcohol or a tertiary aliphatic alcohol. The aliphatic alcohol may be adiol. In some examples, the first solvent is an aliphatic alcoholcontaining 10 carbons or less, for example 8 carbons or less or 6carbons or less. In some examples, the first solvent is an aliphaticalcohol being a diol containing 10 carbons or less, for example 8carbons or less or 6 carbons or less.

In some examples, the first solvent is selected from the groupcomprising 1,2-propanediol, 1,2-butanediol, ethylene glycol,2-methyl-2,4-pentanediol, 1,3-butanediol, 2-methyl-1,3-propanediol and1,3-propanediol. In some examples the first solvent is selected from thegroup comprising 1,2-propanediol, 1,2-butanediol, ethylene glycol,2-methyl-2,4-pentanediol, and 1,3-butanediol. In some examples the firstsolvent is selected from the group consisting of 1,2-propanediol,1,2-butanediol, ethylene glycol, 2-methyl-2,4-pentanediol,1,3-butanediol, 2-methyl-1,3-propanediol and 1,3-propanediol. In someexamples the first solvent is selected from the group consisting of1,2-propanediol, 1,2-butanediol, ethylene glycol,2-methyl-2,4-pentanediol, and 1,3-butanediol. In some examples the firstsolvent is 1,2-butanediol.

In some examples, the inkjet ink composition comprises at least about 1wt % of the first solvent by total weight of the composition, forexample, at least about 5 wt %, at least about 10 wt %, or at leastabout 15 wt % by total weight of the composition.

In some examples, the inkjet ink composition comprises up to about 40 wt% of the first solvent by total weight of the composition, for exampleup to about 30 wt %, or up to about 20 wt % by total weight of thecomposition.

In some examples, the inkjet ink composition comprises the first solventin an amount of from about 1 wt % to about 40 wt % by total weight ofthe composition, for example from about 5 wt % to about 40 wt %, about10 wt % to about 30 wt %, or from about 15 wt % to about 20 wt % bytotal weight of the composition.

In some examples, the ink vehicle of the inkjet ink compositioncomprises a second solvent having a boiling point of at least about 220°C., for example at least about 225° C. In some examples, the secondsolvent has a boiling point up to about 285° C., for example up to about280° C. In some examples, the second solvent has a boiling point in therange of about 220° C. to about 285° C., for example about 225° C. toabout 285° C.

In some examples the second solvent is selected from alcohols (includingaliphatic alcohols and aromatic alcohols), esters, glycol ethers, di-and trialkylene glycols, amides, lactams and sulfones. In some examplesthe solvent is selected from aliphatic alcohols (including primary,secondary and tertiary aliphatic alcohols, including diols), aromaticalcohols, esters, glycol alkyl ethers (such as alkylene glycol alkylethers, including di-, tri- and tetra-alkylene glycol alkyl ethers),glycol aryl ethers (such as alkylene glycol aryl ethers, including di-and tri-alkylene glycol aryl ethers), di- and tri-alkylene glycols,lactams (such as 2-pyrrolidinone) and sulfones (such as sulfolane).

In some examples, the second solvent is selected from aliphatic alcoholscontaining 20 carbons or less (for example aliphatic alcohols containing10 carbons or less), esters containing 20 carbons or less (for exampleesters containing 12 carbons or less), glycol alkyl ethers, such asalkylene glycol alkyl ethers, containing 20 carbons or less (for exampleesters containing 12 carbons or less, or 10 carbons or less), glycolaryl ethers, such as alkylene glycol aryl ethers, containing 20 carbonsor less (for example esters containing 12 carbons or less, or 10 carbonsor less) such as glycol phenyl ethers (e.g. alkylene glycol phenylethers) containing 20 carbons or less, lactams and cyclic sulfones.

In some examples the second solvent is selected from the groupcomprising ethylene glycol 2-ethylhexyl ether, dipropylene glycoln-butyl ether, diethylene glycol n-butyl ether, propylene glycol phenylether, 2-pyrrolidinone, tripropylene glycol methyl ether (such asDowanol™ TPM), 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, triethylcitrate, tripropylene glycol n-propyl ether, tripropylene glycol n-butylether (such as Dowanol™ TPnB), tetraethylene glycol dimethyl ether, anddipropylene glycol phenyl ether. In some examples, the second solvent isselected from the group comprising 2-pyrrolidinone, tripropylene glycolmethyl ether and tripropylene glycol n-butyl ether.

In some examples, the inkjet ink composition comprises at least about0.1 wt % of the second solvent by total weight of the composition, forexample at least about 0.5 wt %, at least about 1 wt %, at least about1.5 wt %, or about 2 wt % by total weight of the composition.

In some examples, the inkjet ink composition comprises up to about 8 wt% of the second solvent by total weight of the composition, for exampleup to about 5 wt %, up to about 3 wt %, or about 2 wt % by total weightof the composition.

In some examples, the inkjet ink composition comprises the secondsolvent in an amount of from 0 wt % to about 8 wt % by total weight ofthe composition, for example about 0.1 wt % to about 8 wt % by totalweight of the composition, from about 0.5 wt % to about 8 wt %, fromabout 0.5 wt % to about 5 wt %, or from about 0.5 wt % to about 4 wt %by total weight of the composition.

Other Additives

The ink vehicle may also comprise a variety of additional components,suitable for inkjet ink compositions, selected from surfactants (forexample suitable surfactants may be selected form alkyl polyethyleneoxides, alkyl phenyl polyethylene oxides, polyethylene oxide blockcopolymers, acetylenic polyethylene oxides, polyethylene oxide(di)esters, polyethylene oxide amines, protonated polyethylene oxideamides, dimethicone copolyols, fluoroalkyl polyethylene oxides,substituted amine oxides, and the like, surfactants when present may bepresent in an amount from 0.01 wt % to 10 wt %), buffers, biocides (suchas Nuosept™ (Nudex® Inc.), Ucarcide™ (Union carbide Corp™.). Vancide™(R. T. Vanderbilt® Co.). Proxel™ (Lonza™) and combinations thereof),viscosity modifiers, sequestering agents (such as EDTA (ethylene diaminetetraacetic acid)), stabilizing agents, wetting agents, and humectants.In some examples, these other additives may be present in a total amountof from 0 wt % to 20 wt %.

Method of Inkjet Printing

Described herein is a method of inkjet printing comprising:

providing a non-porous print substrate; and

inkjet printing an inkjet ink composition to the print substrate to forman ink layer on the print substrate,

wherein the inkjet ink composition comprises a latex polymer and an inkvehicle, wherein the latex polymer is derived from a compositioncomprising a cycloaliphatic monomer and an aromatic monomer, wherein thecycloaliphatic monomer comprises a cycloaliphatic (meth)acrylate monomeror a cycloaliphatic (meth)acrylamide monomer and the aromatic monomercomprises an aromatic (meth)acrylate monomer or an aromatic(meth)acrylamide monomer.

In some examples, the method of printing comprises curing the latexpolymer, for example curing the latex polymer on the print substrate(e.g. non-porous print substrate). Curing of the latex polymer forms afilm of latex on the surface of the print substrate. Curing the latexpolymer to form a film of latex on the print substrate improves thedurability of an image printed using the inkjet ink composition.

In some examples, the ink vehicle comprises water and a co-solvent. Inorder for the latex polymer to be cured, firstly water should beevaporated from the ink layer, then the co-solvent (for example, firstsolvent and second solvent (where present)) should be at least partiallyevaporated from the ink layer such that particles of latex polymer comeinto close contact. Once the particles of the latex polymer come intoclose contact (due to the at least partial evaporation of water andco-solvent) the particles of the latex polymer may coalesce by theintermingling of polymer chains between adjacent latex polymer particlesto cure the latex polymer to from a latex polymer film. In order for thelatex polymer to be cured the temperature must be above the minimum filmformation temperature (MFFT) of the latex polymer. Pigment particles,where present, remain in the ink layer and are embedded within the latexpolymer film on curing of the latex polymer.

Water is evaporated from the printed inkjet ink composition before theco-solvent (e.g. first and/or second solvent) are removed from theprinted inkjet ink composition as water has a higher volatility (e.g.lower boiling point) than the co-solvent.

In some examples, the co-solvent comprises a first solvent and a secondsolvent. In such examples, the first solvent is evaporated, or at leastpartially evaporated, before the second solvent, again due to the highervolatility of the first solvent compared to the second solvent. Thesecond solvent remains in the ink layer after the water has beenevaporated and the first solvent at least partially evaporated.

The present inventors have found that the presence of a co-solventhaving a boiling point of less than about 215° C. (e.g. a first solvent)in the inkjet ink composition allows for fast drying of the inkjet inkcomposition to enable high throughput through a printing system. Thepresent inventors have found that the presence of the second solvent inthe inkjet ink composition which remain in the ink layer afterevaporation of the water and at least partial evaporation of the firstsolvent ensure that the MFFT of the latex polymer remains lowered duringthe curing of the latex polymer.

In some examples, curing the latex polymer comprises evaporating waterfrom the ink layer. In some examples, curing the latex polymer comprisesevaporating water and at least a portion of the co-solvent from the inklayer. Evaporation of water and at least a portion of the co-solventallows latex polymer particles within the ink layer to coalesce into afilm (“cure”). Evaporation may be facilitated in a printing system byproviding heat and/or airflow. Heating may be either conductive,radiative, or convective. Airflow may comprise parallel or impingingairflow. In some examples, heating the ink layer to evaporate water, forexample water and at least a portion of co-solvent comprises heating theink layer such that the temperature of the print substrate is maintainedbelow a temperature at which deformation (e.g. warping) of the printsubstrate occurs. For example, heating the ink layer such that the printsubstrate reaches a temperature of less than about 70° C., for exampleabout 65° C. or less.

In some examples, curing the latex polymer comprises evaporatingsubstantially all of the water from the ink layer, for exampleevaporating at least about 95 wt %, for example at least about 99 wt %,or at least about 99.5 wt % of the water comprised in the inkjet inkcomposition printed as the ink layer. In some examples, curing the latexpolymer comprises evaporating all of the water from the ink layer sothat no water remains in the ink layer.

In some examples, curing the latex polymer comprises evaporating atleast a portion of the co-solvent comprises evaporating a major amountof the co-solvent of the inkjet ink composition printed as the ink layerfrom the ink layer, for example evaporating at least about 80 wt %, atleast about 90 wt %, at least about 95 wt %, or at least about 99 wt %of the co-solvent comprised in the inkjet ink composition printed as theink layer.

In some examples, curing the latex polymer comprises heating the latexpolymer such that latex polymer particles coalesce to form a latexpolymer film. Forming a latex polymer film occurs after evaporation ofwater from the ink layer and at least partial evaporation of the firstsolvent and the second solvent (when present). Forming a latex polymerfilm may comprise heating the ink layer to a temperature greater thatthe MFFT of the latex polymer in the ink layer. In some examples,forming a latex polymer film comprises heating the ink layer to atemperature greater that the MFFT of the latex polymer in the ink layerand a temperature less than a temperature which may cause deformation ofthe print substrate.

In some examples, the method of printing comprises selecting an inkjetink composition such that the MFFT of the latex polymer is below atemperature which may cause deformation of the print substrate. FIG. 1is a schematic diagram of a printing system 100 comprising an inkjetprinter 115 in a printing zone 110 of the printing system 100 and adrier 125 positioned in a curing zone 120 of the printing system 100. Aprint substrate may be transported through the printing system 100 alongthe path shown by arrow A such that the print substrate is first fed tothe printing zone 110 where an inkjet ink composition is inkjet printedonto the print substrate by the inkjet printer 115 (for example from aninkjet cartridge comprising the inkjet ink composition described above)to form an ink layer on the print substrate. The ink layer disposed onthe print substrate may then be heated in the printing zone 110 (forexample the air temperature in the printing zone may range between 10°C. and 90° C.) such that water may be evaporated from the ink layer. Theprint substrate may then be transported to the curing zone 120 where theink layer is heated (for example, the air temperature in the printingzone may range between 10° C. and 140° C.) and air is blown onto theprint substrate (as shown by arrows C) such that the co-solvent is atleast partially evaporated from the ink layer and the latex polymer isheated to a temperature above the MFFT of the latex polymer in the inklayer. In some examples, the printing system 100 comprises a fan 130 forblowing air over the print substrate passing through the printing zone110 to evaporate water from the inkjet layer.

Printed Substrate

Also described herein is a printed substrate comprising a non-poroussubstrate on which an inkjet printed layer is disposed, the inkjetprinted layer comprising a latex polymer, wherein the latex polymercomprises cycloaliphatic monomer and an aromatic monomer, wherein thecycloaliphatic monomer comprises a cycloaliphatic (meth)acrylate monomeror a cycloaliphatic (meth)acrylamide monomer and the aromatic monomercomprises an aromatic (meth)acrylate monomer or an aromatic(meth)acrylamide monomer.

Low energy surface media include polyolefinic media (polypropylene orpolyethylene). These media may be factory modified to facilitate wettingby inks (e.g. aqueous inkjet inks); generally, this modificationincreases the surface energy, but relative to other substrates theyremain ‘low’. Surface energy, for example surface energy with respect toaqueous inks, may be measured by contact angle between the substrate andwater. In some examples, a low energy surface media is a media (i.e.print substrate) having a surface energy of less than about 40 dyne/cm,for example less than about 35 dyne/cm. The surface energy of a printsubstrate may be measured according to ASTM D2578.

While the latex polymers, inkjet ink compositions, methods and relatedaspects have been described with reference to certain examples, it willbe appreciated that various modifications, changes, omissions, andsubstitutions can be made without departing from the spirit of thedisclosure. It is intended, therefore, that the inkjet ink compositions,methods and related aspects be limited only by the scope of thefollowing claims. Unless otherwise stated, the features of any dependentclaim can be combined with the features of any of the other dependentclaims, and any other independent claim.

EXAMPLES

The following illustrates examples of the compositions and relatedaspects described herein. Thus, these examples should not be consideredto restrict the present disclosure, but are merely in place to teach howto make examples of compositions of the present disclosure.

Preparation of Latex Polymer

Example 1—Latex 1

A latex polymer was prepared as follows. Water (138 g) was heated to 77°C. with mechanical agitation. At 77° C., latex seed (4.4 g; 67 nmparticle size) was added to the reactor. At 77° C., potassium persulfate(0.36 g) dissolved in water (4% solution) is added. To this mixture wasadded over 300 minutes: an aqueous emulsion comprised of water (39.4 g),copolymerizable surfactant (Hitenol® AR-10) (4.9 g), cyclohexylmethacrylate (124.6 g), cyclohexyl acrylate (18.0 g), phenoxyethylmethacrylate (25.2 g) and methacrylic acid (7.2 g); and a 4% aqueoussolution (18.3 g) of potassium persulfate.

Residual monomer was reduced using high temperature 85° C. followed by(7.5 g) 5% solution of ascorbic acid and 5% solution of (15.2 g)tert-butyl hydroperoxide at 70° C. After cooling to near ambienttemperature, pH was adjusted to 8 with dilute potassium hydroxide;inkjet suitable aqueous biocides were added. The resulting acrylic latexwas 41% solids by total weight of latex emulsion; particle size 0.22 μm(particle size determined using Microtrac Nanotrac Wave II): viscosity(at 25° C.) less than 50 cp.

Comparative Example 2—Latex 2

Water (116 g) was heated to 77° C. with mechanical agitation. At 77° C.,potassium persulfate (0.30 g) dissolved in water (4% solution) wasadded. At 77° C., latex seed (4.4 g; 67 nm particle size) was added tothe reactor. To this mixture was added over 300 minutes an aqueousemulsion comprised of water (28.2 g), copolymerizable surfactantselected from Hitenol® BC-10, BC-30, KH-05 or KH-10 (1.5 g), methylmethacrylate (91.1 g), styrene (24.1 g), butyl acrylate (4.8 g), andmethacrylic acid (0.6 g).

Residual monomer was reduced as described in Example 1. After cooling tonear ambient temperature, pH is adjusted to 8 with dilute potassiumhydroxide; inkjet suitable aqueous biocides are added. The resultingacrylic latex is 41% solids by total weight of latex emulsion; particlesize 0.22 μm; viscosity less than 50 cp.

Comparative Example 3—Latex 3

Water (138 g) is heated to 77° C. with mechanical agitation. At 77° C.,latex seed (4.4 g; 67 nm particle size) is added to the reactor. At 77°C., potassium persulfate (0.36 g) dissolved in water (4% solution) isadded. To this mixture is added over 300 minutes: an aqueous emulsioncomprised of water (39.4 g), copolymerizable surfactant selected fromHitenol® AR-10, BC-10, BC-30 (4.9 g), cyclohexyl methacrylate (124.6 g),cyclohexyl acrylate (18.0 g), styrene (25.2 g) and methacrylic acid (7.2g); and a 4% aqueous solution (18.3 g) of potassium persulfate.

Residual monomer was reduced as described in Example 1. After coolingthe near ambient temperature, pH is adjusted to ˜8 with dilute potassiumhydroxide; inkjet suitable aqueous biocides are added. The resultingacrylic latex is 41% solids by total weight of latex emulsion; particlesize 0.22 μm; viscosity less than 50 cp.

A black inkjet ink composition was then produced using each of the latexpolymers produced in Example 1 and Comparative Examples 2 and 3. Theformulation of each of the black inkjet ink compositions produced is setout in Table 1 below.

TABLE 1 Amount in grams per 100 g of total inkjet ink compositionComponent Ink 1 Ink 2 Ink 3 1,2-Butanediol 18.00 18.00 18.00 Dowanol ™TPM 2.00 2.00 2.00 Dowanol ™ TPnB 0.70 0.70 0.70 DI Water 39.75 39.7539.75 Wetting agents 2.20 2.20 2.20 Carbon Black 12.84 12.84 12.84Pigment Dispersion Latex 1 24.40 0 0 Latex 2 0 24.40 0 Latex 3 0 0 24.40Testing

Each of Inks 1-3 was tested by inkjet printing each of the inks using alatex inkjet printer directly (i.e. with no primer or pre-treatmentapplied before printing of the inks) onto non-porous and rigidsubstrates, a polypropylene substrate and a vinyl substrate. The inkswere cured at 70° C. following printing on to the polypropylenesubstrate and at 110° C. following printing on to the vinyl substrate. Alower curing temperature was used following printing on thepolypropylene substrate as higher temperatures were found to causewarping of the polypropylene substrate, whereas the vinyl substrate isable to withstand the higher curing temperature.

Samples of each of the printed substrates were subjected to thefollowing three tests. The results are shown in Table 2 below.

Cross Hatch Tape Adhesion Test

The cross hatch tape adhesion test was carried out as defined in ASTMD3359-09 except that Intertape Polymer Group™ 515965 tape was used inplace of Permacel™ P99 test tape. The numbers 1-5 provided in Table 2refer to the amount of latex ink removed from each of the samplesfollowing this test according to the following scale:

Test Scale: 0=0% removed

1=<5% removal

2=5-15% removal

3=15-35% removal

4=35-65% removal

5=>65% removal

Windex® Rub Resistance Test

Windex Blue® window cleaner rub resistance was measured using a Taber®linear abraser model 5750 equipped with an acrylic crockmeter tipcovered with polyester cloth. The cloth was dipped in the rubbing fluid,and the printed image was rubbed 5× with 600 g pressure. Plot damage andwiper cleanliness are graded with the following scale:

Taber Plot Wiper Score Damage Appearance Criteria for Scoring 0 noneclean no damage, no color transfer, clean wiper 0.5 none hint of colorno damage (including gloss), no color loss, faint transfer to wiper 1gloss loss light ink transfer no color loss - only gloss loss, lighttransfer to wiper 2 significant significant 0-20% color loss transfer 3severe significant 20-50% color loss transfer 4 severe significant50-80% color loss transfer 5 severe significant >80% color loss transfer70% 2-Propanol Rub Resistance Test

70% IPA rub resistance was measured using a Taber® linear abraser model5750 equipped with an acrylic crockmeter tip covered with polyestercloth. The cloth was dipped in the rubbing fluid, and the printed imagewas rubbed 5× with 600 g pressure. Plot damage and wiper cleanliness aregraded with the following scale:

Taber Plot Wiper Score Damage Appearance Criteria for Scoring 0 noneclean no damage, no color transfer, clean wiper 0.5 none hint of colorno damage (including gloss), no color loss, faint transfer to wiper 1gloss loss light ink transfer no color loss - only gloss loss, lighttransfer to wiper 2 significant significant 0-20% color loss transfer 3severe significant 20-50% color loss transfer 4 severe significant50-80% color loss transfer 5 severe significant >80% color loss transfer

TABLE 2 IntePro ® Fluted Avery MPI 2903 Inkjet ink PP SAV Vinyl TestFormulation Cured at 70° C. Cured at 110° C. Cross Hatch Ink 1 1 0 TapeAdhesion Ink 2 5 (Fail) 0 Ink 3 5 (Fail) 0 Windex ® Rub Ink 1 0 0Resistance Ink 2 0 0 Ink 3 0 0 70% 2- Ink 1 1 3 Propanol Rub Ink 2 4(Fail) 0 Resistance Ink 3 5 (Fail) 1

The results provided in Table 2 show that Ink 1 containing a latexpolymer according to this invention exhibits improved adhesion anddurability when printed on a range of substrates, for example whenprinted to low energy surfaces such as polypropylene, compared to inkscomprising comparative latex polymers.

The present inventors have also found that inkjet ink compositionscomprising the latex polymer described herein exhibit excellent decapperformance.

While the latex polymers, inkjet ink compositions, methods and relatedaspects have been described with reference to certain examples, it willbe appreciated that various modifications, changes, omissions, andsubstitutions can be made without departing from the spirit of thedisclosure. It is intended, therefore, that the latex polymers, inkjetink compositions, methods and related aspects be limited only by thescope of the following claims. Unless otherwise stated, the features ofany dependent claim can be combined with the features of any of theother dependent claims, and any other independent claim.

The invention claimed is:
 1. A latex polymer comprising a copolymer of acycloaliphatic monomer, an aromatic monomer, and an alkyl (meth)acrylatemonomer, wherein the cycloaliphatic monomer comprises a cycloaliphatic(meth)acrylamide monomer and the aromatic monomer comprises an aromatic(meth)acrylamide monomer, and wherein the latex polymer includes fromabout 60 wt % to about 90 wt % of the cycloaliphatic monomer by totalweight solids of the latex polymer, from about 5 wt % to about 30 wt %of the aromatic monomer by total weight solids of the latex polymer, andfrom about 0.1 wt % to about 10 wt % of the alkyl (meth)acrylate bytotal weight solids of the latex polymer.
 2. The latex polymer accordingto claim 1, the cycloaliphatic monomer having a formula (I):

wherein, R₁ is H or methyl; Z is NR₂, where R₂ is H, alkyl or X′; Y is abond or a C₁₋₁₂ carbon chain where one or more of the carbon atoms ofthe carbon chain may be replaced with a heteroatom selected from oxygen,sulfur and nitrogen; and X and X′ are independently cycloaliphaticmoieties.
 3. The latex polymer according to claim 1, the aromaticmonomer having a formula (II):

wherein, R₁ is H or methyl; Z is NR₂, where R₂ is H, alkyl or W′; Y is abond or a carbon chain, where one or more of the carbon atoms of thecarbon chain may be replaced with a heteroatom selected from oxygen,sulfur and nitrogen; and W and W′ are independently aromatic moieties.4. The latex polymer according to claim 1, the latex polymer having aglass transition temperature in the range of about 40° C. to about 90 °C.
 5. An inkjet ink composition comprising the latex polymer of claim 1,and an ink vehicle.
 6. The inkjet ink composition according to claim 5comprising from about 3 wt % to about 25 wt % of the latex polymer bytotal weight of the inkjet ink composition.
 7. The inkjet inkcomposition according to claim 6 comprising up to about 30 wt % pigmentby total weight of the inkjet ink composition.
 8. The inkjet inkcomposition according to claim 5, wherein the ink vehicle compriseswater and a co-solvent having a boiling point in the range of about 170°C. to about 215° C.
 9. A method of inkjet printing comprising: providinga non-porous print substrate; and inkjet printing an inkjet inkcomposition to the print substrate to form an ink layer on the printsubstrate, wherein the inkjet ink composition comprises the latexpolymer of claim 1 and an ink vehicle.
 10. The method according to claim9, comprising heating the ink layer to cure the latex polymer on theprint substrate.